The present invention relates to an optical information reading apparatus having a two-dimensional imaging visual field for reading a bar code and other one-dimensional codes as well as a QR code and other two-dimensional codes. Furthermore, the present invention relates to an optical information reading method.
Conventionally, for the purpose of administrating merchandise sales and inventories, bar codes and other one-dimensional codes or QR codes and other two-dimensional codes are widely used in various systems. To optically read these codes, conventional optical information reading apparatuses are generally equipped with an area sensor and arranged as a handy type two-dimensional code reading apparatus (i.e. a handy terminal) that enables users to perform a manual reading operation. According to this kind of optical information reading apparatus, a reading section is provided at a front end thereof to enable a user to locate this reading section to the vicinity of a two-dimensional code recorded or printed on a reading objective, such as a catalog, a voucher, and merchandise label. Under this condition, the user operates a trigger switch to cause the reading apparatus to start an image-pickup operation for imaging the two-dimensional code or the like and a reading operation for reading (decoding) the picked-up image of the code.
In recent years, the above-described systems are required to use highly densified codes so that many information codes can be recorded in a limited small area. To satisfy these requirements, there is the tendency that the code reading apparatus uses an area sensor having an increased number of pixels to improve the resolution. However, if two-dimensional codes are downsized, there will be a problem such that a plurality of codes may be simultaneously captured in the same imaging visual field. This is not desirable in that the read processing must be done unnecessarily to read another code that the user does not want to read. Furthermore, such decode processing will take a long time when the pixel number of the area sensor is large.
Meanwhile, there is a conventional reading apparatus that provides a partial region reading mode which enables the apparatus to read only a code located at an intermediate portion of an imaging visual field of an area sensor in the vertical direction. According to this conventional apparatus, it becomes possible to read only a code wanted by a user in a case that plural codes arrayed in a multi-stage pattern are present on a reading objective (for example, refer to the Japanese Patent Application Laid-open No. 2002-92542).
Furthermore, there is another conventional reading apparatus that divides a picked-up image region into a plurality of blocks to effectively detect an existing region of a code in the picked-up image and perform a decoding operation in the detected existing region. According to this conventional reading apparatus, it becomes possible to shorten the processing time (for example, refer to the Japanese Patent Application Laid-open No. 2000-353210 corresponding to the U.S. Pat. No. 6,678,412).
However, in the case of providing the partial region reading mode as described in the Japanese Patent Application Laid-open No. 2002-92542, this mode will be effective in a case that bar codes are aligned in the vertical direction. However, if two-dimensional codes are present next to each other in the right-and-left direction, there will be a problem that selecting a code to be read in a two-dimensional space is difficult. Furthermore, there will be room for further shortening the processing time. According to the latter prior art document characterized by estimating the existing region of such a code, there is also room for improvement in view of shortening of the processing time.